The broad objectives of this proposal are to examine the hypothesis that the more common periodontal infections in HIV+ subjects are caused by specific bacterial or fungal species, which are not necessarily the typical putative periodontal pathogens usually found in comparable periodontal infections in HIV negative subjects. Our preliminary data indicated that HIV+ subjects with necrotizing ulcerative periodontitis (NUP), a more severe periodontal disease unique to these individuals, indeed lacked many of the classical periodontal pathogens, but instead possessed "unusual" taxa, such as Bulleidia extructa and Dialister pneumosintes, and novel "uncultivable" phylotypes of the genera Dialister, Peptostreptococcus, Selenomonas, and members of the "uncultivable" phylum TM7. Our objectives are addressed in two Specific Aims. Aim 1 will identify the predominant cultivable and not-yet-cultivated bacteria and fungi that are associated with periodontal infections in HIV+ subjects, such as gingivitis, low/moderate and severe adult periodontitis, and Linear Gingival Erythema (LGE), another periodontal infection unique to HIV+ subjects. These studies will be performed by analyzing bacterial 16S rRNA and fungal 18S rRNA gene sequences of inserts in clones from plaque libraries. The libraries will be generated by PCR amplification of rRNA genes present in subgingival plaque followed by ligation of the amplicons into appropriate vectors and by transformation of E. coli. The sequence of each clone will be used to determine species identity, or if unknown, its phylogenetic position. It is anticipated that 25 to 50 additional new taxa will be identified. Aim 2 will test the hypothesis that specific bacterial and fungal species are associated with periodontal infections with the deterioration of immune status in HIV+ patients. In each periodontal disease category, 25 subjects with high viral loads and low CD4 levels and 25 subjects with low viral load and high CD4 levels will be analyzed. Comparisons of subgingival microbial and fungal populations will be made between these HIV+ groups vs. control groups of HIV negative subjects. Up to 200 predominant bacterial species will be assayed for each sample using Checkerboard hybridization, which allows for the simultaneous analysis of multiple samples with multiple probes. Up to 30 fungal species will be assayed for each sample in a second, separate checkerboard hybridization. It is likely that specific bacterial complexes (e.g., specific combinations of bacteria/fungi) are associated with these periodontal diseases and may change with the severity of HIV infection. The proposed studies may provide insight for the identity of putative pathogens in comparable periodontal infections in HIV negative individuals.